According to a recent study from Northwestern University, high-performing water filtration systems, which are essential for reducing water scarcity, can also lower costs and energy use. The cost, energy use, and greenhouse gas emissions related to desalination and wastewater treatment were assessed in the new study by performing a high-level analysis of membrane filtration systems. In particular, the researchers looked at antifouling membranes, a high-performance filtration system that prevents contaminants from building up.
Although more expensive at the time of purchase, foul-resistant membranes are less expensive over the course of their lifetimes than less expensive, non-foul-resistant membranes, which need more frequent cleaning and replacement. In fact, the researchers found that municipal wastewater treatment plants could spend up to three times as much on antifouling membranes for desalination and 43% more on antifouling membranes for wastewater treatment and still keep their operating costs at the same level.
Many municipalities and researchers are investigating procedures, such as desalination and wastewater treatment, that can increase water availability from less conventional water resources, like brackish water, as aging infrastructure and climate change stress water supplies. Buying antifouling membranes up front could help bring down the cost of these often expensive treatment systems.
The project’s principal investigator, Jennifer Dunn of Northwestern University, said that technologies like desalination are more critical than ever due to the growing water shortage. However, cost and engineering performance are always tradeoffs. Even if a filtration system performs amazingly, if the price is prohibitive, people won’t use it. Our modeling and analysis are intended to inform future research and development.
On August 15, the study was published in the ACS ES&T Engineering journal. The U.S.-Israel Collaborative Water-Energy Research Center (CoWERC), an international group of universities, water utilities, and private companies that looks for new ways to solve important problems at the intersection of energy and water, has published its first study with international co-authors.
Dunn is the director of the Center for Engineering Sustainability and Resilience and an associate professor of chemical and biological engineering at Northwestern’s McCormick School of Engineering. The paper’s co-first authors are Sabyasachi Das and Margaret O’Connell, both workers in Dunn’s lab.
A membrane serves as a physical barrier between contaminated water and drinkable water in membrane filtration systems. Water is forced through a membrane that has pores that are micron-, nano-, or even smaller in size by pumps. While allowing water to pass through the pores, the membrane captures tiny particles.
Fouling happens when contaminants build up on the membrane’s surface and clog the pores. Higher pressures are required to pump the water through a fouling-prone membrane. But eventually, fouling accumulates to the point where the membrane needs to be cleaned, if not completely replaced. The cost of running a treatment facility can go up if more water pressure, cleaning, and replacing water use more energy and money.
Antifouling membranes, in contrast, have unique surface chemistries that stop contaminants from accumulating. As a result, cleaning is required less frequently, and the membrane lasts longer overall. In their study, the researchers found that lowering operating costs was most affected by extending the life of the membrane.
According to Dunn, this membrane is central to the desalination process. “Anything we can do to extend the life of the membrane or lower cleaning costs will help lower the cost of clean water.”
Dunn hopes that this study will make policymakers, decision-makers, and managers of water treatment facilities aware of the fact that they can afford to use more expensive, higher-performing membranes. This is especially true for desalination facilities, where 65 percent already employ membrane-based filtration techniques.
According to Dunn, there is a payback in terms of decreased energy use and fewer frequent membrane replacements. “If we want to expand the number of desalination plants, we have to do it in a way that doesn’t increase energy use. “Everything is connected.”
